function greet(person: string) {
  return 'hello, ' + person
}

console.log('1.',greet('TypeScript'))

let sym = Symbol()  // Symbol 类型
let obj = {
  [sym]: 'semlinker'
}
console.log('2.',obj)

enum Direction{
  NORTH = 4,
  SOUTH,
  EAST,
  WEST,
}
let dir : Direction = Direction.NORTH
let dirname = Direction[4] // NORTH
let dirVal  = Direction["NORTH"]
console.log('3.',dir,dirname,dirVal)

// let value:unknown
// let value1 : string = value // 终端报错 error
// console.log('4.',value1) 
